~ 
a 
first method is made use of in routine practice when one sus- 
pects that the water is the cause of the spread of cholera. 
The technique is both simple and reasonably accurate, so 
that a negative result may be looked upon as fairly satisfac- 
tory evidence that vibrios are really absent. This remark, 
however, cannot be said to apply to the other pathogenic 
intestinal organisms. It is true that Starkey of McGill Uni- 
versity has proposed a method of separating out and identi- 
fying certain members of the above groups, and although 
admitting the value of his method when a positive result is 
obtained, a negative result is less satisfactory. Again, the 
difficulty in isolating Eberth bacillus from natural water is 
too well known to require anything more than a passing 
reference. Consequently, for ordinary work we have to rely 
for our answer to the two queries, on a study of the natural 
phenomena of the disappearance of fecal organism from 
water. 
Many analysts in England would probably take up the 
position that there are no thoroughly established facts which 
would justify any conclusion on such a point as whether a 
specified pollution was of recent date, or of old standing. They 
would state that whenever fecal organisms are present in 
more than a certain number, that water was dangerous for 
human consumption. Some might go on to say that they 
considered organisms that gave certain fermentative reac- 
tions more objectionable than others which did not. As 
regards England, they are probably correct in making these 
assertions, but we shall show that, in the first place, this atti- 
tude would condemn nearly every drop of drinking-water 
in India, and in the second place, that, thanks to the 
natural conditions of the country, we have got a step further 
than this. 
In practically every laboratory in Europe the presence of 
' *“true coli’’ is accepted as proof of undesirable contamination. 
This coli standard requires some discussion. It is stated by 
Houston that a class of organisms which give certain fermen- 
tative reactions are indicative of objectionable fecal pollution. 
The reactions used are few, and quite a large number of distinct 
species of intestinal organisms fulfil these conditions. We 
